Polycystic ovary syndrome is a common endocrinopathy characterized by chronic anovulation and androgen excess, and an adolescent phenotype has now been identified. The overall hypothesis of this proposal is that insulin resistance is the fundamental pathophysiologic defect in both adolescents and adult females with polycystic ovary syndrome (PCOS), and therefore interventions to improve it are most likely to result in spontaneous ovulation (adults) and reductions in hyperandrogenemia (adolescents). We propose to build on the landmark findings of the Diabetes Prevention Program (DPP), where both a lifestyle intervention and metformin therapy, as single agent therapies, significantly reduced the diabetes conversion rates in a high risk population (the females of which were similar to a PCOS population). We will examine the effects of combination therapy compared to single agent therapy in females with PCOS. The DPP established lifestyle interventions, as the gold standard treatment for this metabolic syndrome and one all affected should receive. Therefore we hypothesized that combination therapy with lifestyle intervention and metformin will be more effective than lifestyle intervention and placebo on improving the stigmata of polycystic ovary syndrome (by 25%). We propose to conduct two parallel trials of this hypothesis: Study 1 will be conducted in an adult population (N = 150, Age 21-39) with ovulation frequency as the primary outcome. Study 2 will be conducted in an adolescent population ( N = 100, Age 14-18) with hyperandrogenemia as the primary outcome. Each study will be a two center, double blind, randomized trial that lasts 6 months. The two treatment strategies: 1) Lifestyle intervention with mefformin, 2) Lifestyle intervention with placebo. We will additionally follow other reproductive and metabolic parameters in both treatment groups for response including acne, hirsutism, glucose tolerance, and body composition. It is unknown if multiple treatments to improve insulin sensitivity are additive in females with PCOS. Additionally there is little data to assess the effects of these combined interventions on improving the hyperandrogenism and anovulation that characterize PCOS. There have also only been very limited studies of these therapies in an adolescent population. Our focus will also specifically be on a minority population and we will also explore ethnic and racial differences in response to therapy.